Fluid displacement machine



c. BANCROFT FLUID DISPLACEMENT MACHINE July 22, 1958 8 Sheets-Sheet 1Filed May 25. 1953 mVzzvnm CHARLES BHNCROFT BY ATTORNEYQ July 22, 1958c. BANCROFT 2,344,040

FLUID DISPLACEMENT MACHINE v Filed May 25. 195: s Sheets-Sheet 2INVENTOR. CHARLES BeNcRoF-r ATTORNEYS July 22,1958 c. BANCROFI' 2,

rwznmsmcmuw momma: Filed May 25. 195: a Sheets-Sheet s' CHARLES BHNCROFTBY l ATTORNEYS IN V EN TOR.

y 22, 1958 c. BANCROFT 2 ,844,040

FLUID DISPLACEMENT MACHINE Fileii ma 25. 1953' v 8 Sheets-Sheet 4 IN VENTOR.

CHARLES BHNCEOF'T HTTORNEYS July 22, 1958 c. BANCROFT 2,

FLUID- DISPLACEMENT MACHINE Filed May 25, 1953 8 Sheets-Sheet 5INVENTOR. CHARLES BANCEOFT QTTOENEYS July 22, 1958 c. BANCROFTY2,844,040

FLUID DISPLACEMENT MACHINE Filed May 25. 1953 s Sheets-Sheet s INVENTOR.CHARLES BFINCROFT BYW/ HTTORNEYS Filed May 25, 1953 8 Sheets-Sheet 7 FEINVENTOR. CHARLES Ba NC ROFT (QTTORNEYS July 22, 1958 c. BANCROFT2,844,040

FLUID DISPLACEMENT MACHINE Filed May 25. 195: I i s Sheets-Sheet 8 IN VEN TOR.

CHARLES BHNCROFT ATTORNEYS United States Patent() 2,844,040 7 FLUIDDISPLACEMENT MACHINE Charles Bancroft, New Canaan, Conn.

Application May 25, 1953, Serial No. 357,160

2 Claims. (Cl. 7452) This invention relates to a fluid displacementmachine adapted for many uses.

One of the objects is to provide a machine design featuring improvedmechanical balance, fewer parts, simplified construction, and greatercompactness and lower cost, than are conventional. Another object is toprovide a construction making possible a multi-cylinder, two cycle,internal combustion engine of improved volumetric efiiciency, whichrequires no valves, other than the pis-' tons themselves, for control ofporting, and which does not require the partitioned crank-caseordinarily characteristic of prior art multi-cylinder two cycle designs.Still another object is to make possible a compact, vibrationless gasgenerator of relatively simple construction, or, alternately, anexceptionally compact, eight cylinder, four cycle engine, usingrelatively few moving parts, or an unusually compact, multi-cylinder,pump. Other objects will become apparent from the following.

The invention involves the use of reciprocatory pistons requiring acrank-shaft arrangement. In developing this arrangement advantage hasbeen taken of the fact that when a second crank-shaft is rotatablymounted on the crank-pin of a crank-shaft of equal crank-throw radius,and is controlled in its rotation on that crank-pin so that it rotatesat a speed, relative to the stationary main body of the unit, equal andopposite to that of the crankshaft on which it is mounted, itscrank-pins reciprocate in straight lines intersecting the axis ofrotation of the latter crank-shaft. When the pistons are rotatablymounted at their gravitational centers of these crank-pins, they can beconfined within cylinders in which they will reciprocate through astroke equal to twice the sum of the crank-throw radii of the twocrank-shafts although all of the mechanical movements involved arepurely rotary and can be balanced as such.

Since, when two crank-shafts are employed together as described above,the crank-pins of the second crank-shaft will move in straight linesintersecting the axis of the first or supporting crank-shaft;conversely, it follows that if two or more crank-pins of the secondcrank-shaft are forcibly restrained to such linear motion, as forexample by pistons mounted on the crank-pins being confined withinsuitable cylinders, that crank-shaft will both be supported in itsmovement through the circle which it follows on the crank-pin of thefirst crank-shaft and will also be restrained to the opposite and equalrotation, while moving through that circle, which the circumstancesrequire. Thus it follows that the pistons mounted on the crank-pins ofthe second crank-shaft act as supporting bearings for that crank-shaftand also control, or assist in controlling, that crank-shafts rotationon the crankpin of the first crank-shaft.

Specific examples of mechanisms and machines embodying the principles ofthe invention are illustrated by the accompanying drawings in which:

Fig. 1 is a perspective view showing an example of two sets of pistonsprovided with the type of crank organization described but constructedand arranged in accordance with the present invention;

Fig. 2. is a cross section showing the assembly of Fig. 1 in use in amachine which may be used as a two cylinder, two cycle gasoline engine;

Fig. 3 is a section taken substantially on the line 3-3 in Fig. 2;

Fig. 4 is a section taken substantially on the line 44 in Fig. 3;

Fig. 5 is a view similar to Fig. 2 excepting that it shows theprinciples of the invention applied to a machine adapted to function asa gas generator useful for operating turbines and the like; i 1

Fig. 6 is a section taken substantially on the line 6-6 in Fig. 5;

Fig. 7 is a view similar to Fig. 2 but showing a machine which may beused as a four cylinder, two cycle gasoline engine, this incorporating amodification of the arrangement shown by Fig. 1;

Fig. 8 is a section taken substantially on the line 88 in Fig. 7.

In the assembly shown by Fig. l, the described second crank-shaft is inthe form of an intermediate crank-shaft having oppositely extendingshafts 1, single-throw crankarms 2 and double-throw crank-arms 3, withcrank-pins 4 extending between the arms 2 and 3, in each instance, and acrank-pin 5 extending between the arms 3, the latter being formed as apair of spaced arms. The crank-arms are aligned with each other, thecrank-pins 4 are eccentric to the shafts 1, and the crank-pin 5 iseccentric to the shafts 1 opposite to the crank-pins 4. The displacementof the crank-pins 4 and 5 relative to the shafts 1 are equal andopposite.

The shafts l oppositely extend through bearing holes 6 formedeccentri-cally in two shafts 7 of large diameters with the axialdisplacement of the shafts 1 relative to the axes of the shafts 7 beingequal to the axial displacement of the crank-pins 4 or 5 relative to thecrank-shaft 1. The shafts '7 are completely separate from each other andfunction as cranks mounting the crank-shaft previously described. Thisor an equivalent arrangement provides adequate room for proper bearingsfor the shafts 1 of the crank-shaft. The outer ends of the shafts 7 arereduced and cut-out to provide room for pinions 8 secured to the outerends of each of the shafts 1. When these pinions 8 are engaged bystationary ring gears of proper diameter and axially concentric with theshafts 7, rotation of the shafts 7 in one direction results in oppositerotation of the intermediate crank-shaft under the control of thepinions 8, and therefore the crank-pins 4 and 5 move linearly inintersecting paths.

The pistons are made as two sets of oppositely facing pistons 99 and14)10. The inner or back ends of the pistons 9 are rigidlyinterconnected by laterally spaced struts 11 which may be externallycontoured as continuations of the cylindrical piston sides, whereby toin effect form a double-ended piston having a central slot. The strutsmay be centrally divided transversely and the parts clamped together bylong screws 12 so as to form bearings journalling the struts 11 to thetwo crank-pins 4. The spacing between the struts 11 is sufficient forrotation of the arms 3. The inner ends of the pistons 10 areinterconnected by a single strut 13 in a rigid manner, and this strut 13may also be centrally split transversely with the parts held together byscrews so as to form a bearing journalling the strut 13 to the crank-pin5, or, as shown by the drawings, the strut may be solid and thecrank-pin 5 made as separate parts projecting from the crank-arms 3 andbolted together in the manner common to radial engine crank-pins.

When the pistons are arranged in right angularly related cylinders thepistons and their interconnecting struts are firmly guided to follow thereciprocating paths of the respective crank-pins, whereby theintermediate crankshaft is supported rotatively. By making the twohalves of each piston set so that the crank-pin journal bearings are atthe center of gravity of the piston set, in each instance, it becomespossible to balance the moving parts as purely rotary parts even thoughthe pistons reciprocate. The forces involved are purely rotary inefiect. This effect is obtained when single pistons are journaled toeach crank-pin, instead of the sets, when there is enough overhangingweight to make the center of gravity of each piston coincide with itscrank-pin, and the piston is adequately guided linearly.

Referring now to Figs. 2 through 4, the pistons are shownreciprocatively positioned in a set of opposed cylinders and 16, and thepistons 9 reciprocatively positioned in a set of opposed cylinders 17and 13. Each set of cylinders is radially arranged at right angles toeach other. The cylinders are mounted by a crankcase 19 which completelyencloses the crank-shaft assembly and is provided with axial holes inwhich the respective shafts 7 are journaled in bearings 20. Thecrank-case 19 outwardly extends axially from the radial walls in whichthe shafts 7 are journaled. End plates 21 are secured to the ends of thecrankcase extensions 19a and these end plates immovably mount thepreviously described ring gears, shown at 22, with which the pinions 8are constantly meshed as the pinions revolve due to rotation of theshafts 7. The shafts 7 are continued outwardly with reduced portions 23forming journals mounted by bearings 24 in the end plates 21, the latterhaving holes 25 through which the outermost ends of the shafts 7 extendas at 26.

Due to the fact that the pinions 8 force the crank shaft 1 to rotate onits axis in the same fashion at both ends, the individually separateshafts 7 are rotatively locked together so that they function as asingle shaft in which the crank-shaft 1 is eccentrically journalled.Neither of the shafts 7 can rotate independently of the other, theeffect being that of a single crank-shaft formed as two rotativelyinterconnected halves. It is to be noted that the shaft 7 function ascranks having their outer ends journalling the crank-shaft 1 andrevolving about axes common to the axes of the shafts 7.

The cylinders 15 and 16 have their outer ends closed and provided withthreaded holes 27 in which spark plugs may be screwed to fully enclosethese ends. The

outer ends of the cylinder 17 and 18 are completely closed by cylinderheads 28 in each instance.

The crank-case19is made with its previously described radial walls,which mount the bearings 20, in the form of hollow walls. space insideof these hollow walls, the spaces 30 being interconnected as to bothcrank-case bearing-mounting end walls. The crank-shaft arrangement issuch that the pistons 9 diifer in angular phase from the pistons 16during the operation of the machine. In the illustrated form the phasedifference is 90 and, therefore, when one piston set is stationary ateither of its reciprocating extremes, the other piston as at itsmid-position and moving at its maximum velocity.

In Figs. 2 through 4 the cylinders 15 and 16 and the pistons 10 funtionas a two-cycle internal combustion engine, and the cylinders 17 and 18and pistons 9 function as a scavenging blower for this engine. Passagesfrom the cylinders 17 and 18 feed into the inner ends of the cylinders15 and 16 where they are alternately either connected by slots in thepistons 10 with the intake manifold space 30 or, when the pistons areout of the way, directly with the crank-case. Thus the pistons 10control the intake and output of what is in effect a scavenging blowerformed by the cylinders 17 and 18 and the pistons 9. Since the pistons10 are moving at their maximum velocities when the blower is shiftedfrom input to out put, the valve action is rapid, which is advantageous.

A fluid intake passage 29 leads to the The blower output is thus fedinto the crank-case from which it discharges into the cylinders 15 or 16through passages opening into these cylinders and uncovered by thepistons when at their inner limits, whereby to both scavenge and chargethese cylinders. Suitable exhaust ports are uncovered by the pistons atthis time, as is usual. Additional intake passages for the scavengingblower cylinders 17 and 13 may be arranged to open from the intakemanifold so that they are uncovered when the pistons 9 are at theirinner limits. In such instances as when the valving action is at the endof a passage connecting with the cylinder, the volume of the passage isadded to that above the piston during the compression phase, and thefeatures of the present invention permit such passage to be made veryshort with a consequent ability to effect adequate volumetricefiiciency.

With the foregoing in mind, the intake manifold space 30 connects withthe portion of the cylinder 16 that is inner respecting the center ofthe engine, through ports 31, and with the inner portion of the cylinder15, respecting the engine center, through ports 32. Both of the pistons10 are provided in their side walls with longitudinally extendinggrooves 33 which register with the ports 31 and 32 as either pistonapproaches and is adjacent to its innermost limit, or in other words,throughout the inner half of its piston stroke.

The cylinder 16 has ports 34 spaced inwardly from the port 31 and withwhich the latter is connected by the grooves 33 when the latter registerwith the ports 31. These ports 34 connect with a passage 35 leading intothe outer end of the cylinder 17, as shown by Fig. 2. The cylinder 15has comparable ports 36 connecting with a passage 37 leading into theouter end of the cylinder 18. An exhaust port 38 is located in thecylinder 16 so as to be uncovered by the piston when the pistonapproaches and is adjacent to its innermost position, this port 38connecting with an, exhaust passage 39. The cylinder 1.5 has acomparable exhaust port 40 connecting with an exhaust passage 41.

The ports 34 and 36 and their respective passages 35 and 37 are in partshown in broken lines in Fig. 2 only so as to indicate their locations.As shown in Fig. 3 there are three of these ports in each instance andthe outer two are diametrically located for registration by the pistongrooves. The passages 35 and 37, as the case maybe, extend as asemi-circle portion from the outer two ports, around behind therespective cylinder walls, and thus to the straight portions leading tothe cylinders 17 or 18 in each instance. Referring to Fig. 3, thesemi-circle portion of the passage 35 is in a plane above that of thedrawing, as is indicated in Fig. 2 which also shows that the semi-circleportion of the passage 37 is below the plane of the drawing so it can beindicated by the broken lines in Fig. 3. In each instance, the centerone of the ports 34 or 36 are in effect auxiliary ports which functionwhen the charge is blown into the crank-case as subsequently described.

The crank-case interior connects with the cylinder 16 through a passage42 and a port 43 located through the cylinder wall diametricallyopposite to the exhaust port 39. The crank-case, in a similar manner,connects with the cylinder 15 through a passage 44 and a port 45.Preferably, the cylinders 17 and 18 have auxiliary ports 45a connectingwith the intake manifold space 30 and located in each instance so as tobe uncovered by the piston as the latter approaches and is at itsinnermost limit.

In operation the intake passage 29 is connected with a carburetor or thelike for supplying a suitable corn.- bustible mixture, and, of course,spark plugs will be located in the holes 27 and energized by a suitablytimed sparking voltage. 'Upon proper rotation of the shafts 7 the chargeis sucked through the intake manifold 30, which would be by theleft-hand piston 9 asthe operation is shown by Fig. 2, through the ports31 and 34, by way of the registering piston grooves 33 of the piston inthe cylinder 16, and thus into the cylinder 17 from the head ofwhich thepistons 9 are retreating. As the operation continues the pistons 9reverse so as to compress the charge. In the drawings this compressionis underway in the cylinder 18, which was previously sucked full of thecharge. The compressed charge is driven through the passage 37 and intothe crank-case, the piston in thecylinder being now clear of the ports36. The compressed charge in the crank-case drives in through thepassage 42 and port 43 into the cylinder 16.

Thus in succession the charge is appropriately introduced to. thecylinders so as to scavenge them free from burnt gases and provide themwith fresh charges. As the appropriate one of the pistons 10 advances itcuts off all of the ports ahead of its working face and goes into itscompression phase ready for firing. After firing, the exhaust is, ofcourse, through the ports 38 and 40 or the exhaust passages 39- and 41,as the case may be.

It can now be seen that in a single compact unit the set of pistons 9provide the previously described scavenging blower with its valve actioncontrolled bythe working pistons so as to eliminate valves as such. Thecrankcase is used as part ofthe fiuid transfer system but it is notrequired to operate alternately under sub-atmospheric andsuper-atmospheric pressure, so there is no need for separating webs ordiaphragms in the crank-case for any reason. The spaces between theradial crankcase-walls and the end plates 21 provide gear cases for the'pinions 8 and ring gears 22 and may be flooded with lubricant asdesired. The crank-shaft 1 and pinions 8 are balanced by counterbalances46, and the gear box space also provides room in which thesecounterbalances may move. Referring now to the gas generator, shown byFigs. 5 and 6, the same fundamental parts and principles are usedas havebeen described in connection with the example shown by Figs. 2 through4. Therefore, wherever possible the same numerals are used to identifycorresponding parts and where these parts are modified the same numeralsare used in conjunction with a letter.

In this gas generator the piston 10 in the cylinders 15.

and 16 function to power the pistons 9a in the cylinders 17a;and 18a,the pistons 91: and the last-named cylinders being of much largerdiameter than are shown in connection with the first example for thecorresponding scavenging blower parts. Another difference is that theintake system is modified by the provision of intake passages 29adirectly in the heads of each of the cylinders 17a and 18a,respectively, these intake passages being provided with poppet checkvalves 47.

. As to the operation of this second example, the lefthand pliston 9a isshown moving to the right and sucking air in through the passage 29a,the poppet check valve 47 being sucked open to permit this. Therighthand one of the pistons 9a is on its compression stroke and isforcing a large volume of air, previously sucked in as described,through the passage 37 and port 36 into the crank-case. The upper one ofthe pistons 10 has cleared the port 36 at this time, the piston havingformerly blocked this port in the manner the lower one of the pistons 10is shown doing in the case of the port 34, as required to close thepassage 35 during the suction stroke. From thecrank-case the air drivesup through the passage 42 and out of the port 43 so as to L scavenge andcool the cylinder'16 and from therethrough the exhaust port 41 mixedwith the hot products of previous combustion, a residue of air beingleft in the-cylinderto charge it for the next compression. In this casethe passage 42 surrounds all of the cylinders so as to be heated therebyand to cool the cylinders by the air moving through the passage 42.

The upper one of the pistons 10 is at the limit of its compressionstroke. Because there is an excess of air involved this example showsthe use of solid fuel injection nozzles 48 so that the machine operatesin the 6 manner of a diesel. Asuitable fuel injection control must, ofcourse, be provided.

This second example is particularly adapted to produce a large volume ofhighly compressed gas which may be used, by connections to the exhaustports 41, for powering a turbine or the like. The pistons 9a work aspumps compressing large volumes of air into the passage 42 surroundingthe cylinders and thus into the power cylintders above the pistons 10where the air is heated by the combustion,. as to the portionof the airretained by the cylinders, so as to obtain a relatively high temperaturebeforebeing mixed with 'fresh scavenging air and discharged through theexhaust ports. The principles of the present invention provide for acompact and smooth operating unit capable of being controlled easily andwhich produces a large volume of hot compresed gas.

The four cylinder, two cycle, gasoline engine illustrated by Figs. 7 and8 involves a modification of the crank-shaft and piston assemblies shownby Fig. 1.

In this modification the intermediate crank-shaft involves the use oftwo eccentrics 3a and 3b, instead of the crank-arms 3 of the firstexample. All of the power pistons 10a, of which there are four, areorganized in the form of sets of two pistons each with the vertical onesinterconnected by a rigid piston rod 13a journaled on the eccentric 3aand the horizontal ones interconnected by a rigid piston rod 13bjournaled on the eccentric 3b. This arrangement provides a' fourcylinder radial engine requiring somemeans for scavenging and rechargingthe cylinders above the pistons. This is provided for as describedbelow.

A vertical scavenging blower piston set 9a reciprocates with its pistonheads respectively in the cylinders 15 and 16, the pistons beingapertured so as to permit the sliding passage of the rod 13. This pistonset 9a has the inner ends of its respective pistons interjoined by astrut 11a having a central cross head 49 in which a block 50transversely reciprocates. This block 50 is journaled on an eccentric 51fixed to the inner end of the left-hand one of the shafts 7 as viewed inFig. 8. The horizontal set of the scavenging blower pistons 9b areinterconnected by a strut 11b provided with a similar cross head 4% inwhich a block 50a reciprocates and is journaled on an eccentric 51afixed on the inner end of the righthand one of the shafts 7. Horizontalpistons 9b are also apertured to slidingly pass the piston rod 13b. Thecrank-case 19a is made in rectangular fashion so that it may beinternally provided with suitable guiding surfaces for supporting thetwo cross heads in their relatively right angular motions and in linewith their respective piston sets.

The described assembly is timed so that the power piston sets 10aare outof phase with each other and so that the scavenging blower pistons 9aeach lags in phase behind its associated power piston by 90.Furthermore, the eccentrics 51 and 51a are contoured so that in eachinstance the stroke of the blower piston is shorter than the powerpiston stroke.

'Each cylinder and its two pistons functions the same as the other 'sothe following description is applicable to all. In each instance eachcylinder has an intake port 52 opening into its inner end so as to becleared by the porting piston 9a or 9b when the latter approaches and isat the limit of its innermost stroke limit. As shown in the right-handone of the horizontal cylinders in Fig. 7, this results in sucking acharge, as from a carburetor, into the space formed between the twopistons 9b and 10b. As the action continues the piston 9b advances, asshown in the case of the cylinder 17, while the piston 10b is movinginwardly. Each cylinder has a transfer passage 53 opening into thecylinder through an inner port 54 and an outer port 55 respectivelylocated so that one or the other is. closed by the adjacent piston 9bwhen the latter is at either of its stroke limits or adjacent thereto,but so as to span-the piston 9b'when' the latter is 7 at an intermediateposition. Therefore, as the pistons 9b and 10b move, so as to diminishthe space between them, as shown on the left-hand side of Fig. 7", thecompressed charge is transferred to the crankcase.

In Fig. 7 the upper ones of the pistons 9a and 10a: are shown nearly attheir closest positions, respecting each other, and at this time atransfer passage 56 is opened because it has an inlet port 57 positionedto be cleared by the piston 9a at this time, and an outlet port 58cleared by the pistons 10a, whereby the charge is transferred from thecrank-case to above the power piston so as to scavenge the cylinderthereabove and recharge it ready for compression and firing. The exhaustaction after firing is readily apparent.

In all of the foregoing examples it is to be understood that thoseskilled in the art can effect the necessary timing as to the ignitionmeans in the case of the gasoline type and the fuel injection in thecase of the diesel type. The three examples serve to illustrate how theassembly of Fig. 1 permits the designing of unusually compact fluiddisplacement machines which may be balanced as though comprising onlyrotary parts. The invention further provides for the scavenging blowerswith their necessary valve action provided by the power pistons with theresulting valve action rapidly inaugurated and terminated, due to theoscillatory motion imparted each piston and the timing alreadyexplained. i

It is to be understood that all of the piston sets are centrallyjournaled to the crank-arms, whether provided by arms as such or byeccentrics, at the centerof gravity of the piston set in each instance.Furthermore, the pistons and their interconnecting members, as to eachset, are rigidly guided linearly by the cylinders in which the pistonsreciprocate, whereby to rotationally support they intermediatecrank-shaft in all instances, due to. there being a plurmityintersecting lines or paths through which the crank-pins or theirequivalent reciprocate and which represent truly rotary motions. Withproper rotary balancing smooth operation results. It is to beunderstoodthat by interconnecting the two spaced shafts as described, the rigidguiding by the cylinders is not absolutely necessary.

It is to be noted that where the valving of one cylinder is controlledby the piston of another cylinder, onset radially substantially 90, asshown by the drawings, the mid-point in time of any valving condition inthe controlled cylinder occurs when the controlling piston is at the topor bottom of its stroke, and, therefore, if the valve timing is changedat one end of the stroke of the piston in the controlled cylinder, thereshould be a corresponding change in the valve timing at the other end ofthe stroke since the mid-point duration of port opening or closing mustalways correspond to the top or bottom of the stroke of the controllingpiston.

If then, as may be true in the case of the piston gas generator shown bythe drawings, it is preferable to have the pumping cylinders connectionto the output manifold (in this case the crank-case area) delayed duringthe output stroke of the pumping pistons until the pressure in tnesecylinders reach that already existing in the crankcase section, formingthe output manifold, and to have this connection broken, as before, atthe end of each output piston stroke, it can be seen that the mid-pointof duration of such a port opening would not coincide with the top orbottom of the stroke of the controlling piston.

- However,- by changing the radial angular relationship. of

the controlled cylinder to that of the cylinder in which the controllingpiston works, the top or bottom of the stroke can be made to coincidewith the mid-point of the port opening duration as. required; It isexpressly understood that such variations in the radial angularrelationship of the various sets of pistons can. be introduced for suchpurposes or other purposes, without effecting the basic principles ofthis invention, as described here, or their advantages, such as thebalancing advantages, etc;

It is also to be understood that while the invention is illustrated byexamples having the crank-case section acting as a connecting manifoldbetween the scavenging pumps and the control cylinders, other examplescan be constructed to have the crank-case section acting as apreliminary intake manifold or eliminated entirely from any function inconnection with the passage of working fluids through the unit. Also,although all the drawings included herewith relate to four cylinderunits, or an equivalent construction, any number of crank-pins and setsof pistons can be employed to provide any number of working cylinders ina single row or multi-row construction or to provide single cylinder, inline, or V-type units.

To simplify the description, reference hasbeen made herein to singleports in instances where the drawings show a multiplicity of openings,to etfect loopscavenging forexample. It is to be understood, therefore,that herein a reference to a port is to be construed as meaning a singleopening or a group of interconnected openings.

I claim:

1. A fluid displacement machine including a plurality of sets of opposedcylinders arranged radially about an axis, a piston in each of thecylinders, struts laterally spaced axially respecting said axis andinterjoining the pistons in one of the cylinder sets, a strut positionedbetween the spaeed struts and interjoining the pistons inanotherof thecylinder sets, cranks journaled to rotate onsaid axis and positioned onopposite sides of the spaced struts and having arms revolving about saidaxis, and a crank-shaft journaled by and between the cranks arms andhaving crank-arms on the outside of the spaced struts withcrank-pins'extending therefrom and journaled to and extending throughthe struts and double crank-arms between the struts and which are joinedby a crank-pin journaled to and extending through the strutpositionedbetween the spaced struts.

2-. A fluid displacement machine including a plurality. of sets ofopposed cylinders arranged radially about anaxis, a piston in each ofthe cylinders, struts laterally spaced axially respecting said axis andinterjoining the pistons in one of'the cylinder sets, a strut positionedbetween the spaced struts and interjoining the pistons inanother of thecylinder sets, cranks journaled to'rotate onsaid axis and positioned onopposite sides of the spaced struts and having arms revolving about saidaxis, andacr-ank-shaft journaled by and between the cranks arms andhaving crank-arms on the outside of the spaced strutswith' crank-pinsvextending therefrom and journaled to and extending through the strutsand double crank-arms be-- tween the struts and which are joined by acrank-pin journaled to and extending through the strut positionedbetween the spaced struts, the cranks and crank-arms hav-- ing equaleffective lengths, and means for causing the cranks to rotatesynchronously together and for causing opposite rotation of thecrank-shaft, whereby the crankpins move through intersecting linearpaths while supported rotatively by the pistons and struts.

References Cited in. the file of this patent UNITED STATES PATENTS1,056,746 Pitts Mar. 18, 1913 1,585,453, Williamson May 18; 1926,1,761,429. Dean June 3, 1930 1,774,105 Nelder "Aug. 26, 193.0 1,787,599Stickney Jan. 6,. 1931 2,088,863 McClelland' Aug. 3, 1,937 2,132,595Bancroft Oct. 11, 1938 2,199,625; Fiala-Fernbrugg n, May, 7, 1940;2,223,100 Foster Nov. 26, 194.0,

FOREIGN PATENTS 341,010 Great Britain July 4, 1929 884,403; France Apr.27, 1943.

